Semiconductor device fabrication and dry develop process suitable for critical dimension tunability and profile control

ABSTRACT

The critical dimension (CD) of features formed during the fabrication of a semiconductor device may be controlled through the use of a dry develop chemistry comprising O 2 , SO 2  and a hydrogen halide. For example, a dry develop chemistry comprising a gas comprising O 2  and a gas comprising SO 2  and a gas comprising HBr may be used to remove exposed areas of a carbon-based mask. The addition of HBr to the conventional O 2  and SO 2  dry develop chemistry enables a user to tune the critical dimension by growing, trimming and/or sloping the sidewalls and to enhance sidewall passivation and reduce sidewall bowing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to semiconductor fabrication processesand, more particularly, to dry develop processes with improvedtunability of critical dimensions during semiconductor fabrication.

2. State of the Art

A common process requirement in semiconductor device fabrication is theremoval of material layers or films to form features of a semiconductordevice. For example, semiconductor fabrication may include the etchingand formation of structures and openings such as trenches, contacts andvias in the material layers overlying conductive or semiconductivesubstrates. The patterning and formation of such structures is generallyaccomplished through the use of a patterned photolithographic mask andoften, a hard mask or resist.

During semiconductor fabrication, it is preferable for sidewalls of themask and resist used to define desired features to remain perpendicularto the surface of the underlying substrate. However, as featuredimensions are ever-decreasing and desired feature densities areever-increasing, it is more and more difficult to create complex circuitstructures on a small size chip using conventional etching processes.For example, as the size of the photoresist or photomask patterns arereduced, the thickness of the photomask must also decrease, in order tocontrol pattern resolution in the underlying layers. The thinnerphotomask is not very rigid and may be eroded away during the etchingprocess, which may lead to sidewall bowing (i.e., concave sidewalls) inthe photomask and to poor line and profile control, as well as loss ofthe critical dimension of the mask and underlying substrate.

One approach to solve this problem of mask erosion is to include anantireflective coating (ARC) beneath the photomask. The ARC is formedover the substrate layers to be etched to prevent non-uniform reflectionof radiation during the patterning of the photomask and, thus, inhibitdefects in the photomask. Subsequently, the ARC may be etched using thephotomask layer as a mask to remove those layers of the ARC whichcorrespond to the openings in the photomask. However, even with the useof an ARC, there may still be lateral etching and sidewall bowing usingconventional etching processes.

In another approach to the mask erosion problem, a carbon-based mask maybe formed above an underlying semiconductor substrate and beneath thephotomask and/or ARC as an etch-stop layer in order to improve thefidelity of the masking layers during etching of the underlyingsubstrate layers. The carbon-based mask is more rigid and etch resistantthan the photomask layer, thus providing for good etch selectivity forfabrication of openings in the semiconductor device.

Conventional plasma dry etch gas chemistries include CHF₃+CF₄+O₂+Ar,N₂+He+O₂, N₂+O₂, N₂+He, O₂+CO₂, O₂+SO₂, and C₂F₆+Ar. This type of plasmaetching is called a “dry develop” process. Dry develop processchemistries, such as O₂+SO₂, are known in the art and work well, as theygive good selectivity to the mask material and the underlying layer.However, conventional dry develop process chemistries lack sufficientability to tune the critical dimension (CD) of the mask bypreferentially growing, trimming or slanting the sidewall profile of acarbon-based mask. Furthermore, when the critical dimension of the maskfalls below 120 nm, it becomes advantageous or even necessary to useadvanced patterning and etching techniques. The critical dimension of amask includes the profile and dimensions of the features of a mask suchas the dimensions of the patterned solid regions as well as thedimensions of the exposed and removed areas of the mask. For example, itmay be advantageous to grow (i.e., add material to), to trim (i.e.,remove material from) and/or slant a surface defining a criticaldimension of the carbon-based mask and, as such, tune the criticaldimension thereof.

Therefore, there is a need for a dry develop process providing theability to tune and control critical dimensions of a carbon-based maskduring the fabrication of semiconductor devices.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming that which is regarded as the present invention,the features and advantages of the claimed invention can be more readilyascertained from the following description of the invention when read inconjunction with the accompanying drawings in which:

FIGS. 1 a and 1 b illustrate a cross-sectional view of a semiconductorsubstrate covered with a carbon-based mask and an initial maskstructure;

FIG. 2 illustrates a cross-sectional view taken from FIG. 1 followingthe removal of exposed photomask areas with the non-exposed photomaskareas remaining;

FIG. 3 illustrates a cross-sectional view taken from FIG. 2 followingthe removal of exposed areas of an anti-reflective coating with thenon-exposed areas of the anti-reflective coating remaining;

FIG. 4 illustrates a cross-sectional view taken from FIG. 3 following apartial removal of the exposed areas of a carbon-based mask;

FIGS. 5 a and 5 b illustrate a cross-sectional view taken from FIG. 4following a completed removal of the exposed areas of a carbon-basedmask;

FIG. 6 shows compiled results from experiments 1-8;

FIGS. 7-14 are scanning electron microscopy (SEM) cross-sections showingthe critical dimension profiles of the wafers for each of theexperiments 1-8;

FIGS. 15-20 illustrate the fabrication of semiconductor device featureswhile using a pitch-doubling process; and

FIG. 21 is a schematic representation of a plasma reactor which may beused to carry out the processes of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to various embodiments of a methodof fabricating a semiconductor device, examples of which are illustratedin the accompanying drawings. Although the following description refersto the illustrated embodiments, it is to be understood that theseembodiments are presented by way of example and not by way oflimitation. The following detailed description encompasses suchmodifications, alternatives, and equivalents as may fall within thespirit and scope of the invention as defined by the claims.

It is to be understood that the processes described herein do not covera complete process flow for the fabrication of a semiconductor device.Processes that incorporate teachings of the present invention may bepracticed with various semiconductor device fabrication techniques thatare conventionally used in the art, and only so much of the commonlypracticed process acts are included herein as are necessary or desirableto provide an understanding of the present invention. Thus, for example,the following description does not address the interconnection of thetransistors formed or other subsequent processing, generally referred toas “back end” processing.

In one aspect, the invention includes methods of tuning the criticaldimension of semiconductor device features formed during thesemiconductor fabrication process. The methods may include the use of adry develop chemistry comprising O₂, SO₂ and a hydrogen halide. Themethods may further include supporting a semiconductor device in a drydevelop reactor and forming a carbon-based mask 15 m over thesemiconductor device. As illustrated in FIGS. 1 a and 1 b, the methodsmay also include forming an initial mask structure 20 on a carbon-basedlayer 15 and patterning the initial mask structure 20 to form exposedareas 18 and non-exposed areas 19 of the initial mask structure 20. Theinitial mask structure 20 may include a photomask 17 and one or moreARCs 16. The ARCs 16 may be an organic bottom antireflective coating(BARC) used alone, or in combination with, an inorganic ARC such as asilicon oxynitride, which may also be referred to as a dielectricantireflective coating (DARC).

Additionally, the methods of one aspect of the invention may includeremoving the exposed areas 18 of the initial mask structure 20 with anappropriate removal process in order to expose an area of thecarbon-based layer 15, as shown in FIG. 3. The exposed area of thecarbon-based layer 15 may be removed to form the carbon-based mask 15 m(see, FIGS. 4 and 5 a) using a dry develop process comprising supplyinga gas including O₂, a gas including SO₂ and a gas including a hydrogenhalide to the dry develop reactor. FIGS. 1 a and 1 b illustrate howinitial structure 5 may be supported in a dry develop reactor 6. Acarbon-based layer 15 may overlay the semiconductor device structure 30.An initial mask structure 20 may be formed over the carbon-based layer15. The initial mask structure 20 may include exposed areas 18 andnon-exposed areas 19.

In another particular aspect of the invention, a dry develop chemistrycomprising O₂, SO₂ and HBr may be used to remove the exposed areas 18 ofthe carbon-based mask 15 m to create openings 45 (see FIGS. 2-5 b). Theaddition of HBr to the conventional O₂ and SO₂ dry develop chemistryenables a user to tune the critical dimension by growing and/or trimmingthe sidewalls 40. Moreover, the O₂, SO₂, HBr dry develop chemistry maybe used to enhance passivation of sidewalls 40 and reduce bowing ofsidewalls 40, thus improving the fidelity of the critical dimension andallowing fabrication of structures such as transistor gate structureswith line widths equal to or less than 120 nm (see FIGS. 5 a and 5 b).Also, for purposes of example only and not as a limitation, the O₂, SO₂,HBr dry develop chemistry may be used to form features with extremelyhigh aspect ratios (ratio of feature height to width) of up to 20:1 or25:1 or even greater. Furthermore, the use of the O₂, SO₂, HBr drydevelop chemistry allows for a higher etch rate and greater selectivityof the carbon-based layer 15.

Conventional dry develop chemistries containing O₂ and SO₂ without HBroften result in the lateral etching and bowing of sidewalls 40 and lossof the critical dimension. The term “critical dimension loss,” as usedherein, includes the erosion of feature dimensions during the etchingprocess such as bowing of feature sidewalls and lateral etching of theoverlying mask structure. This phenomenon is caused, at least in part,by the higher reactivity of alternate dry develop chemistries withreactants such as O⁻, Cl⁻, and F⁻ that will etch the sidewall 40 withoutproviding sufficient passivation of the sidewall 40. However, using theO₂, SO₂, HBr dry develop chemistry allows for a user to tune theprofiles of sidewalls 40 and provides for passivation of sidewalls 40,thus limiting lateral etching and sidewall bowing typically exhibited bythe use of dry develop chemistries without HBr.

Passivation of the carbon-based mask 15 m, such as passivation of thesidewalls 40, occurs as the Br⁻ ions react with the sidewalls 40 of thecarbon-based mask 15 m forming a passivation layer, such as a layer ofCBr₄, on the surface of the sidewalls 40 (see, FIG. 4). The volatilityof CBr₄ is less than the volatility of CF₄ and CCl₄ layers that may beformed with the use of alternate dry develop chemistries. Additionally,the CBr₄ passivation layer on the vertical sidewalls 40 of openings 45is more resistant to removal by impinging ions from the dry developchemistry than the more horizontal surfaces on the bottoms of openings45. For example, without the CBr₄ passivation layer, O⁻ ions wouldremove the sidewalls 40 along with the exposed areas at the bottom ofopenings 45 of the carbon-based mask. However, passivation of sidewalls40 with the O₂, SO₂, HBr dry develop chemistry promotes selectiveetching of the carbon-based mask 15 m on the bottoms of openings 45(FIG. 4) while preserving the profiles of the sidewalls 40.Additionally, passivation of sidewalls 40 by CBr₄ improves theselectivity and resolution of subsequent etching of the underlyingexposed areas of the semiconductor device structure 30.

Examples of processes of the present invention may be carried out by adry develop process run in a dry develop reactor or a plasma etchreactor, such as a Lam 2300 KIYO etcher (Lam Research Corporation,Fremont, Calif.). Furthermore, particular embodiments may use low orhigh density systems. According to one aspect of the invention, the drydevelop process may begin with an initial structure 5 (FIGS. 1 a and 1b) supported by a dry develop reactor 6. As known by those in the art,the dry develop process may proceed by energizing the dry developchemistry gases into a plasma state and removing the exposed areas 18 ofthe initial mask structure 20. Referring to FIGS. 2-4, the dry developprocess proceeds as the exposed areas 18 are removed from the initialmask structure 20 and the carbon-based mask 15 m. As illustrated inFIGS. 5 a and 5 b, the dry develop process may proceed until the exposedareas 18 of the initial mask structure 20 and the carbon-based mask 15 mare removed, thus, revealing the underlying semiconductor devicestructure 30 through the openings 45.

Referring to FIGS. 1 a and 4, features may be formed in a carbon-basedmask 15 m while maintaining the critical dimension as patterned by aninitial mask structure 20. The carbon-based layer 15 and thecarbon-based mask 15 m may include amorphous carbon or transparentcarbon. Without limiting the scope of the present invention, thecarbon-based layer 15 may have a thickness of about 1000 angstroms toabout 7000 angstroms, although use of carbon-based masks of othersuitable thickness are also within the scope of the present invention.The carbon-based layer 15 may be formed by a chemical vapor deposition(CVD) process or by other methods known in the art. The carbon-basedlayer 15 may be overlaid with an initial mask structure 20 that maycomprise a patterned photomask 17 and one or more ARCs 16, such as aBARC or a DARC, or combinations thereof. The one or more ARCs 16 areconventionally used to provide better control of the photolithographicprocess wherein a pattern of exposed areas 18 and non-exposed areas 19are created in the photomask 17 (FIGS. 1 a and 2). The pattern in thephotomask 17 may comprise an initial template for features of asemiconductor device structure 30. The patterned exposed areas 18 andnon-exposed areas 19 of photomask 17 may also define the formation ofopenings 45 in the carbon-based mask 15 m by a dry etch or a dry developprocess (see, FIGS. 5 a and 5 b). The carbon-based mask 15 m may be usedto transfer the pattern of openings 45 to an underlying material layer14 of semiconductor device structure 30. The initial mask structure 20may be used to etch the carbon-based layer 15 directly or it may be ahard mask that may, in turn, be used to etch the carbon-based layer 15.

In another embodiment, an intermediate mask layer 60 may, for purposesof example only and not as a limitation of the present invention,comprise one or more oxide 61, polysilicon 62, oxide 63 hard mask layers(FIG. 1 b) and may be deposited over a carbon-based layer 15. Referringto FIG. 5 b, the polysilicon 62 or the oxide 61 may act as an etch-stopin forming the intermediate mask 60 m. Also, the intermediate mask layer60 may be a hard mask disposed between a photomask 65 and thecarbon-based layer 15. As shown by FIG. 1 b, a patterned photomask 65may be deposited over the hard mask layers comprising oxide 61,polysilicon 62, and oxide 63 in order to pattern exposed areas 18 andnon-exposed areas 19. The exposed areas 18 of the hard mask layerscomprising oxide 61, polysilicon 62, oxide 63, exposed through aperturesof the photomask 65, may be removed by an appropriate process to exposethe underlying carbon-based layer 15. As shown by FIG. 5 b, the exposedareas of the carbon-based layer 15 may then be removed by a dry etchprocess to form an intermediate mask 60 m comprising a carbon-based mask15 m and the pattern of openings 45 to expose the underlyingsemiconductor device structure 30. Once a suitable initial maskstructure 20 m (FIG. 3) or an intermediate mask 60 m (FIG. 5 b) has beenformed by known processes, a carbon-based mask 15 m may be definedtherewith.

The carbon-based mask 15 m may be formed by dry etching a carbon-basedmaterial using an etch chemistry comprising O₂, SO₂, and HBr. Such achemistry may be referred to as a dry develop process. As the drydevelop process proceeds, as shown in FIGS. 2-4, the relative ratios ofthe gases may be adjusted in order to grow, trim or otherwise change thesidewall 40 profile of the opening 45 to maintain the desired criticaldimension. For example, the flow rate of HBr may be increased toincrease the growth rate of material deposition, whereas O₂ flow ratemay be increased to enhance sidewall etching.

In another embodiment of the present invention, the O₂, SO₂, HBr drydevelop chemistry may be used in processes for forming an intermediatehard mask that may provide for even greater dimensional control whenforming a carbon-based mask from which one or more features of asemiconductor device are to be defined.

For purposes of example only and not by way of limitation of the presentinvention, the O₂, SO₂, HBr dry develop chemistry may be used for aso-called “pitch doubling” process during the formation of semiconductordevices. Pitch doubling is generally used to increase the number offeatures on a semiconductor device by making a mask with double thelinear density that may conventionally be obtained withphotolithographic processes.

During a pitch doubling process, an initial negative mask layer 50 (see,FIG. 15) may be formed over a carbon-based layer 15. With continuedreference to FIG. 15, initial negative mask layer 50 may be formed bysequentially forming a hard mask layer 48 and a negative carbon-basedlayer 51 over the carbon-based layer 15 and a semiconductor devicestructure 30 that may be exposed through the carbon-based mask 15 m.Hard mask layer 48 may comprise one or more layers of any materialsuitable for use as a hard mask, such as polysilicon, an oxide, asilicon nitride, a silicon oxynitride, a silicon carbide, SiCN, Al₂O₃,or the like. Hard mask layer 48 is employed as an etch stop and a hardmask for subsequent material removal processes. Initial negative masklayer 50 may comprise a negative carbon-based layer 51 made fromtransparent carbon (TC), amorphous carbon, or the like. Alternatively,one or more ARCs 49 may be formed over negative carbon-based layer 51.ARC 49 may comprise one or more BARC or DARC layers or a combination ofBARC and DARC layers.

As shown in FIG. 15, a photomask 52 may be formed over initial negativemask layer 50 and negative carbon-based layer 51 as well as over otheroptional layers to facilitate patterning of one or more layers of hardmask layer 48 and the negative carbon-based mask 51 m (FIG. 17).Photomask 52 may be applied and patterned by known processes.

The general pattern of photomask 52 may be transferred to the underlyingnegative carbon-based layer 51 by etching the ARC 49, as illustrated inFIG. 16. Etching ARC 49 may also shrink the critical dimension of thephotomask 52. Any suitable process, including, without limitation, knownetching processes (e.g., dry develop processes, etc.), may be used tosubstantially transfer the pattern of photomask 52 to negativecarbon-based layer 51.

The exposed areas of the negative carbon-based layer 51 may be removedusing an O₂, SO₂, HBr dry develop chemistry process. The O₂, SO₂, HBrdry develop chemistry provides a high etch rate of the negativecarbon-based layer 51 and high selectivity to the one or more ARCs 49layer. Furthermore, the O₂, SO₂, HBr dry develop chemistry is superiorto the typical O₂ and SO₂ chemistry because of the ability to tune andcontrol the critical dimension and form vertical sidewalls 40 (FIG. 17).Hard mask layer 48 may act as an etch stop during the removal of theexposed negative carbon-based mask 51 m.

Once an initial negative mask layer 50, comprising the negativecarbon-based mask 51 m, has been formed, any remnants of photomask 52may be removed, as known in the art (e.g., with a suitable maskstripper) and shown in FIG. 17.

Next, as depicted in FIG. 18, an oxide layer 54 (e.g., doped or undopedsilicon dioxide, etc.) is formed over the negative carbon-based mask 51m structure and portions of hard mask layer 48 that are exposed throughthe initial negative mask layer 50. Oxide layer 54 may be formed by anysuitable process, including, but not limited to, deposition techniques,spin-on techniques, and the like.

After oxide layer 54 is formed, a spacer etch may be conducted, asillustrated in FIG. 19. As familiar to those of ordinary skill in theart, a spacer etch is an anisotropic etch process. Hard mask layer 48may act as an etch stop during the spacer etch process. The spacer etchprocess removes the relatively thin portions of oxide layer 54,including portions thereof that are located over the remaining regionsof the negative carbon-based mask 51 m, as well as portions of the oxidelayer 54 that are located over the hard mask layer 48, between adjacentremaining regions of the negative carbon-based mask 51 m. The thickerregions of oxide layer 54, which are adjacent to the lateral edges ofthe remaining regions of the negative carbon-based mask 51 m, are notremoved. The result is the spacer mask 56 as illustrated in FIG. 19.

The remaining regions of the negative carbon-based mask 51 m (FIG. 19),which are exposed through the spacer mask 56, are removed by suitableprocesses, as shown in FIG. 20. For example, the remaining regions ofthe negative carbon-based mask 51 m may now be removed using a O₂, SO₂,HBr dry develop chemistry or other suitable etching process.

Thereafter, also as depicted in FIG. 20, regions of hard mask layer 48that are exposed between portions of spacer mask 56 may be removed. Theexposed portions of the underlying carbon-based layer 15 may be removedusing an O₂, SO₂, HBr dry develop chemistry, as discussed previously,because of its high etch rate of the carbon-based layer 15 and theability to trim and/or grow the critical dimension of the carbon-basedlayer 15. The carbon-based layer 15 and the carbon-based mask 15 m maybe made from transparent carbon, amorphous carbon, or the like. Theremaining portions of hard mask layer 48, the overlying spacer mask 56and the underlying carbon-based mask 15 m collectively form a hard mask58, through which patterning of the semiconductor device structure 30and underlying structures may be effected (FIG. 20).

In order to demonstrate the effects of the O₂, SO₂, HBr dry developchemistry on the critical dimension of a carbon-based mask, tests werecarried out in a chamber 102 of a Lam 623 dry etch reactor 100,schematically depicted in FIG. 21, with the temperature held at 40° C.inner and outer temperatures, and the pressure held at 5 mTorr. The dryetch reactor 100 includes a planar antenna 114 which inductively couplesradio-frequency (RF) energy into the reactor through a dielectric window110. A semiconductor substrate 116 is supported on a substrate support118 which may include a bottom electrode for applying an RF bias to thesemiconductor substrate 116. The test results are shown in TABLE 1 andFIG. 6. For TABLE 1 and FIG. 6, TCP represents the top power or thepower in watts applied to the antenna 114, BP represents the bottompower or the power applied to the bottom electrode, the gas flow rates(O₂ Flow, SO₂ Flow, HBr Flow) are listed in units of standard cubiccentimeters per minute (sccm), CD represents critical dimensionmeasurement in nanometers (nm), CD bot-top represents the difference incritical dimension from the bottom to the top of the profile in nm andER is the etch rate of the transparent carbon mask in angstroms perminute (Å/minute). FIGS. 7-14 are SEM cross-sections showing thecritical dimension profiles of the wafers for each of the experiments1-8, respectively, as described in TABLE 1.

FIG. 7 is a SEM of experiment 1 showing the bottom (64.3 nm) and top(48.6 nm) measurements of the critical dimension for a feature in acarbon-based mask after using the O₂, SO₂, HBr dry develop chemistry.The conditions of experiment 1 are shown in TABLE 1. The SEM of FIG. 8shows the results of experiment 2 (see, TABLE 1) and, when compared toFIG. 7, demonstrates how the critical dimension may be tuned by changingthe conditions of the dry develop process. FIGS. 9-14 are SEMscorresponding to experiments 3-8 from TABLE 1, respectively, andillustrate the ability to tune the critical dimension by using differentratios of O₂, SO₂, and HBr during the dry develop process.

TABLE 1 Ex- peri- CD ment Wafer TCP BP O₂ SO₂ HBr CD bot-top ER 1 18 300100 10 30 75 63.4 14.7 1154 2 19 500 100 30 30 25 45.1 11.3 2486 3 20300 200 10 50 25 60 15.8 1740 4 21 500 200 10 30 25 57.5 15.8 2320 5 22500 200 30 50 75 56.4 6.8 2677 6 23 300 200 30 30 75 60.2 10.2 1832 7 24300 100 30 50 25 50.8 13.6 1740 8 25 500 100 10 50 75 65.7 15.9 1740

As shown by TABLE 1 and FIG. 6, the test results indicate that as thegas flow rates for O₂, SO₂ and HBr are adjusted, the etch rate (ER), thecritical dimensions (CD) of a carbon-based mask will also change. Assuch, the ER and the critical dimension, including the sidewall 40profile, may be tuned and controlled by regulating the dry developprocess conditions. For example, referring to TABLE 1, the maximum ERwas achieved during experiment 5 with gas flow rates of O₂ at 30 sccm,SO₂ at 50 sccm, and HBr at 75 sccm. Referring to FIG. 6, the middle CDrow, illustrating the changes in the critical dimension for differentgas flow rates, it is evident, for example, that as the HBr flow ratesincrease, the critical dimension measurements or profile may also bechanged.

While the present invention has been described in terms of certainillustrated embodiments and variations thereof, it will be understoodand appreciated by those of ordinary skill in the art that the inventionis not so limited. Rather, additions, deletions and modifications to theillustrated embodiments may be effected without departing from thespirit and scope of the invention as defined by the claims that follow.

1. A method of fabricating a semiconductor device comprising: forming amask comprising carbon over a semiconductor device structure; forming apreliminary mask comprising photoresist over at least a portion of themask; and exposing surfaces of the mask comprising carbon exposedthrough the preliminary mask comprising photoresist to a dry developetch chemistry comprising O₂, SO₂, and at least one hydrogen halide toremove at least a portion of the mask comprising carbon and form atleast one feature in the mask comprising carbon; and adjusting a ratioof the at least one hydrogen halide to the O₂ in the dry develop etchchemistry during exposure of the surfaces of the mask comprising carbonto control a critical dimension of the at least one feature in the maskcomprising carbon.
 2. The method of claim 1, wherein adjusting a ratioof the at least one hydrogen halide to the O₂ in the dry develop etchchemistry during exposure of the surfaces of the mask comprising carboncomprises adjusting at least one of a flow rate of the at least onehydrogen halide and a flow rate of the O₂.
 3. The method of claim 1,wherein forming a preliminary mask comprising photoresist comprisesforming a photomask over at least one antireflective coating.
 4. Themethod of claim 3, wherein forming a photomask over at least oneantireflective coating comprises forming the photomask over at least oneof an organic bottom antireflective coating (BARC) and an inorganicdielectric antireflective coating (DARC).
 5. The method of claim 1,wherein adjusting a ratio of the at least one hydrogen halide to the O₂in the dry develop etch chemistry during exposure of the surfaces of themask comprising carbon comprises controlling a relative flow rate ofeach of a gas comprising the O₂, a gas comprising the SO₂, and apassivating gas consisting of the at least one hydrogen halide to tunethe critical dimension of the at least one feature in the maskcomprising carbon during the removal of material from the maskcomprising carbon.
 6. The method of claim 1, wherein exposing surfacesof the mask comprising carbon exposed through the preliminary maskcomprising photoresist to a dry develop etch chemistry comprising O₂,SO₂, and at least one hydrogen halide comprises exposing surfaces of themask comprising carbon exposed through the preliminary mask comprisingphotoresist to a dry develop etch chemistry comprising O₂, SO₂, and HBr.7. The method of claim 1, wherein exposing surfaces of the maskcomprising carbon exposed through the preliminary mask comprisingphotoresist to a dry develop etch chemistry comprising O₂, SO₂, and atleast one hydrogen halide comprises introducing a gas comprising the O₂into a chamber at a flow rate of from about 10 sccm to about 30 sccm,introducing a gas comprising the SO₂ into the chamber at a flow rate offrom about 30 sccm to about 50 sccm, and introducing HBr into thechamber at a flow rate of from about 25 sccm to about 75 sccm.
 8. Amethod of forming an opening in a mask comprising: forming a maskcomprising carbon; forming a preliminary mask comprising photoresistover the mask comprising carbon; exposing at least one area of the maskcomprising carbon exposed through the preliminary mask comprisingphotoresist to a gaseous reactive species derived from O₂ and SO₂ toform at least one opening in the mask comprising carbon; exposing the atleast one opening formed in the mask comprising carbon to a gaseouspassivating species derived from HBr to form a passivation materialcomprising CBr₄ on at least one surface of the at least one opening; andadjusting a concentration of the gaseous passivating species withrespect to the gaseous reactive species during exposure of the at leastone opening formed in the mask comprising carbon to control a criticaldimension of the at least one opening.
 9. The method of claim 8, whereinexposing at least one area of the mask comprising carbon exposed throughthe preliminary mask comprising photoresist to a gaseous reactivespecies derived from O₂ and SO₂ to form at least one opening in the maskcomprising carbon comprises exposing the at least one area of the maskcomprising carbon exposed through the preliminary mask comprisingphotoresist to the gaseous reactive species derived from the O₂ and theSO₂ to form at least one opening having a width of less than or equal toabout 120 nanometers.
 10. The method of claim 8, wherein exposing the atleast one opening formed in the mask comprising carbon to a gaseouspassivating species derived from HBr comprises forming the passivationmaterial comprising the CBr₄ on surfaces of sidewalls of the at leastone opening.
 11. The method of claim 8, wherein forming a maskcomprising carbon comprises forming a mask comprising carbon having athickness of between 1000 angstroms and 7000 angstroms.
 12. A method oftuning at least one critical dimension of a feature of a maskcomprising: forming a mask comprising carbon over a semiconductor devicestructure; forming a preliminary mask over the mask; exposing at leastone area of the mask comprising carbon exposed through the preliminarymask to a dry etch chemistry comprising O₂, SO₂, and a hydrogen halideto remove material from the mask comprising carbon to form at least onefeature in the mask comprising carbon; and changing a concentration ofthe hydrogen halide in the dry etch chemistry during exposure of the atleast one area of the mask comprising carbon to tune a criticaldimension of the at least one feature in the mask comprising carbon. 13.The method of claim 12, wherein exposing at least one area of the maskcomprising carbon exposed through the preliminary mask to a dry etchchemistry comprising O₂, SO₂, and a hydrogen halide comprisesintroducing a gas comprising the O₂, a gas comprising the SO₂, and a gascomprising HBr into a chamber, each of the gas comprising the O₂ and thegas comprising the SO₂ introduced at a flow rate less than a flow rateof the gas comprising the HBr.
 14. The method of claim 12, whereinexposing at least one area of the mask comprising carbon exposed throughthe preliminary mask to a dry etch chemistry comprising O₂, SO₂, and ahydrogen halide comprises introducing a gas comprising the O₂ into achamber at from about 10 sccm to about 30 sccm, introducing a gascomprising the SO₂ into the chamber at about 30 sccm to about 50 sccm,and introducing a passivating gas consisting of the at least onehydrogen halide into the chamber at about 25 sccm to about 75 sccm. 15.The method of claim 12, wherein changing a concentration of the hydrogenhalide in the dry etch chemistry during exposure of the at least onearea of the mask comprising carbon comprises adjusting a rate at whichmaterial is removed from the mask comprising carbon.
 16. A method offabricating a semiconductor device comprising: forming a mask comprisingcarbon over a semiconductor device structure; forming a negative maskover the mask comprising carbon; forming a photomask over the negativemask; removing at least one area of the negative mask exposed throughthe photomask; forming a spacer mask over the mask; removing at leastone area of the negative mask exposed through the spacer mask; exposingat least one area of the mask comprising carbon exposed through thespacer mask to a gaseous reactive species derived from O₂ and SO₂ toremove material from the mask comprising carbon to form a recesstherein; exposing the recess formed at the at least one area of the maskcomprising carbon to a gaseous passivating species derived from at leastone hydrogen halide to form a passivation material on a surface of therecess; and adjusting a ratio of the gaseous passivating species derivedfrom the at least one hydrogen halide to the gaseous reactive speciesderived from O₂ and SO₂ during exposure of the recess formed at the atleast one area of the mask comprising carbon to control a criticaldimension of the recess in the mask comprising carbon.
 17. The method ofclaim 16, wherein forming a negative mask over the mask comprisingcarbon comprises forming a negative mask comprising at least one ofamorphous carbon and transparent carbon over a hard mask overlying themask comprising carbon.
 18. The method of claim 16, wherein removing atleast one area of the negative mask exposed through the photomaskcomprises exposing the at least one area of the negative mask to thegaseous reactive species derived from at least the O₂ and the SO₂ toform an opening therein and exposing the opening formed at the at leastone area of the negative mask to the gaseous passivating species to formthe passivation material on a surface of the opening.
 19. The method ofclaim 18, wherein exposing the opening formed at the at least one areaof the negative mask to the gaseous passivating species to form thepassivation material on a surface of the opening comprises exposing theopening formed at the at least one area of the negative mask to agaseous passivating species derived from HBr to form a passivationmaterial consisting of CBr₄ on sidewalls of the opening.
 20. The methodof claim 16, wherein adjusting a ratio of the gaseous passivatingspecies derived from the at least one hydrogen halide to the gaseousreactive species derived from O₂ and SO₂ during exposure of the recessformed at the at least one area of the mask comprising carbon to controla critical dimension of the recess in the mask comprising carboncomprises controlling a flow rate of a gaseous passivating gasconsisting of HBr to tune the critical dimension of the recess in themask comprising carbon during the removal of material from the maskcomprising carbon.
 21. The method of claim 20, wherein: exposing atleast one area of the mask comprising carbon exposed through the spacermask to a gaseous reactive species derived from O₂ and SO₂ comprisesintroducing a gas comprising the O₂ into a chamber at a flow rate offrom about 10 sccm to about 30 sccm and introducing a gas comprising theSO₂ into the chamber at a flow rate of from about 30 sccm to about 50sccm; and exposing the recess formed at the at least one area of themask comprising carbon to a gaseous passivating species derived from atleast one hydrogen halide comprises introducing a gas consisting of theleast one hydrogen halide into the chamber at a flow rate of from about25 sccm to about 75 sccm.
 22. The method of claim 16, wherein exposingthe recess formed at the at least one area of the mask comprising carbonto a gaseous passivating species derived from at least one hydrogenhalide comprises exposing the recess formed at the at least one area ofthe mask comprising carbon to a gaseous passivating species derived froma passivating gas consisting of HBr.
 23. The method of claim 22, whereinexposing the recess formed at the at least one area of the maskcomprising carbon to a gaseous passivating species derived from apassivating gas consisting of HBr comprises controlling a flow rate ofthe passivating gas to tune the critical dimension of the recess formedat the at least one area of the mask comprising carbon during theremoval of material from the mask comprising carbon.
 24. The method ofclaim 23, wherein: exposing the at least one area of the mask comprisingcarbon exposed through the spacer mask to a gaseous reactive speciesderived from O₂ and SO₂ comprises introducing a gas comprising the O₂into a chamber at a flow rate of from about 10 sccm to about 30 sccm andintroducing a gas comprising the SO₂ at a flow rate of from about 30sccm to about 50 sccm; and controlling a flow rate of the passivatinggas comprises introducing the passivating gas into the chamber at a flowrate of from about 25 sccm to about 75 sccm.
 25. The method of claim 16,wherein forming a photomask over the negative mask comprises forming thephotomask over an antireflective coating overlying the negative mask.26. A method of fabricating a semiconductor device comprising: forming amask comprising carbon over a semiconductor device structure; forming apreliminary mask comprising an oxide, polysilicon, and oxide hard maskover the mask comprising carbon; forming a photomask over thepreliminary mask; removing at least one area of the preliminary maskexposed through the photomask; exposing at least one area of the maskcomprising carbon exposed through the preliminary mask to a dry etchchemistry comprising O₂, SO₂, and a hydrogen halide to remove at least aportion of the mask comprising carbon, forming at least one feature inthe mask comprising carbon; and adjusting a concentration of thehydrogen halide in the dry etch chemistry during exposure of the atleast one area of the mask comprising carbon to control a criticaldimension of the at least one feature in the mask comprising carbon. 27.The method of claim 26, wherein exposing at least one area of the maskcomprising carbon exposed through the preliminary mask to a dry etchchemistry comprising O₂, SO₂, and a hydrogen halide comprises exposingthe at least one area of the mask comprising carbon exposed through thepreliminary mask to a dry etch chemistry comprising O₂, SO₂, and HBr.28. The method of claim 27, wherein adjusting a concentration of thehydrogen halide in the dry etch chemistry during exposure of the atleast one area of the mask comprising carbon to control a criticaldimension of the at least one feature in the mask comprising carboncomprises controlling a flow rate of a passivating gas consisting of HBrto tune the critical dimension of the at least one feature in the maskcomprising carbon during the removal of material from the maskcomprising carbon.
 29. The method of claim 28, wherein controlling aflow rate of a passivating gas comprises introducing the passivating gasinto a chamber at a flow rate of from about 25 sccm to about 75 sccm.